Question

Cats make good house pets, although I like snakes better. The main clause is

Answer 1

Cats make good house pets...
this is the answer because of the main idea in the sentence.
Although is the dependent clause because it's depending on the main idea to provide follow up information

Answer 2

Cats make good house pets. It's the main idea in the sentence, and it's independent also. The other clause is dependent, so it is not the main clause.